Error Message: VPN Connection Error 800: Unable to Establish Connection

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Article ID: 319108 - View products that this article applies to.
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When you try to establish a virtual private network (VPN) connection, you may receive the following error message:
Error 800: Unable to establish connection


This issue may be caused by a router that has outdated firmware. For example, this issue may occur if you are using a Cisco router with firmware that is dated 2000 or earlier.

To verify that this is the cause, look at a network trace. The Cisco device advertises a 0 window size in the TCP handshake on port 1723.


To resolve this issue, contact the manufacturer of the router for possible upgrades.

More information

For additional information about how to configure VPN connections in Windows XP, click the article numbers below to view the articles in the Microsoft Knowledge Base:
314076 HOW TO: Configure a Connection to a Virtual Private Network
305550 HOW TO: Configure a VPN Connection to Your Corporate Network in Windows XP Professional


Article ID: 319108 - Last Review: January 8, 2014 - Revision: 2.0
Applies to
  • Microsoft Windows XP Home Edition
  • Microsoft Windows XP Professional
kberrmsg kbprb KB319108

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